AdBlue System Failure Prevents Audi A5 From Starting

Dealt with a similar AdBlue system failure on my 2015 Audi A3 2.0 TDI. The service light came on first, followed by multiple diesel exhaust system warnings. The engine eventually refused to start. The root cause was a faulty dosing unit, not just empty AdBlue fluid. When the AdBlue stops flowing correctly between tank and dosing module, the emissions control system triggers a safety lockdown. This prevents engine starts to maintain emission standards compliance. The repair required: Complete system diagnosis, Replacement of the dosing module, Cleaning of crystallized AdBlue deposits, Reset of the emission control unit, Fresh AdBlue fluid This was a serious repair that kept the car at the garage for 3 days. The system needs proper maintenance to prevent similar issues. Regular AdBlue top-ups are essential, waiting until the tank runs completely dry can damage components. Running without AdBlue is not an option on modern diesel vehicles. The dashboard alert warnings should never be ignored as they indicate potential system damage beyond just low fluid levels.

Thanks for sharing your experience with the AdBlue issue. Dealing with a very similar problem on my A5 right now. The SCR catalyst and injection system needed attention too when they checked it. Just wondering, do you remember roughly what you paid for the full repair? Also, has the system worked properly since the fix or have you noticed any other problems with the emissions control?

Since getting my A3 fixed last month, the injection system has worked flawlessly. The main problem was indeed the AdBlue tank output being defective, causing issues with the dosing unit. The total repair cost was 250 Euro, which covered both parts and labor. The diesel exhaust system now functions exactly as intended, with no more dashboard alerts or service lights appearing. Fuel efficiency has actually improved slightly since the repair, which was an unexpected bonus. To prevent future problems, I now monitor the AdBlue levels regularly and dont let the tank run completely empty. The mechanic explained that maintaining proper fluid levels helps protect the entire emissions control system from damage. No issues have occurred since the repair, and the engine starts perfectly every time. Just make sure to use quality AdBlue fluid when refilling, it makes a difference in how the system performs long-term.

After the initial issues with my A5, I finally got it sorted at the mechanic last week. The DEF fluid system needed a complete overhaul, they found crystallized deposits blocking the injection system. The service light had been warning me for weeks, but I kept putting it off. The repair took 2 full days. They had to flush the entire system, replace the dosing module, and recalibrate the emissions control unit. Tank capacity was restored to normal after cleaning out all the old residue. Total cost came to 280 Euro, which actually wasnt as bad as I feared. Fuel efficiency has improved noticeably since the fix. The engine starts right up now with no warning lights. Lesson learned, will definitely keep an eye on the AdBlue levels from now on. The mechanic showed me how to check it properly and recommended regular top-ups to prevent future system damage.